In many fields of application, there is the need to measure surfaces of objects, and therefore also the objects themselves, with high accuracy. This applies in particular for the manufacturing industry, for which the measurement and checking of surfaces of workpieces is very important. To this end, there is a multiplicity of approaches, which range from contacting methods to optical sensors, in which electromagnetic radiation is used for the measurement.
Usually, a sensor element specific to the respective measurement task is in this case fastened on the measuring machine by means of a coupling. Such sensor elements typically have a probe component with a probe element, which is guided over the surface to be measured and, in the tactile case, touches the surface and measures this surface by generating or maintaining the contact. In the so-called sampling method, or with touch-trigger probes, a switching process is triggered by generation of a mechanical contact with the surface. Such solutions are known, for example, from EP 1 617 171.
As an alternative or in addition, however, contactless optical measurement of the surface may also be carried out, in which case the probe element has a beam path for the measurement radiation and emits this radiation in the direction of the surface and receives it again.
For both measurement methods, owing to the configuration of the probe element, unintended contact or contact associated with excessively high forces in the sense of a collision is disadvantageous and to be avoided. On the one hand, this may be achieved by low speeds and accelerations during the movement of the probe component, although this entails longer measurement times. It is therefore known in the prior art to provide sensor elements with collision protection by virtue of their design, which in the event of unintended contact with a surface avoids or reduces damage to the sensor element, or to the workpiece to be measured, by tilting or release of the probe component.
To this end, in the prior art, sensor elements which attract the probe component mechanically or electromagnetically onto the bearing of a probe component coupling are mostly used, the direction of the force pointing away from the probe element and in the direction of the coupling to the measuring machine, which is also referred to as the so-called z direction or z axis. This arrangement allows simple construction by using electromagnets or permanent magnets and springs. In the event of a lateral collision, the probe component can then tilt relative to the probe component coupling, and either be released or folded back again after a countermovement has been initiated.
For example, EP 2 161 536 discloses an optical sensor with collision protection for a measuring machine, which comprises a sensor-side coupling part for mechanical and optical connection to the measuring machine, and a sensor element. The sensor has a sensor protection coupling as collision protection with a coupling part on the measuring machine side and a coupling part on the sensor element side, the coupling being carried out by the attraction force of magnets or a pulling, i.e. prestressed, tension spring. In the event of a collision, the coupling is opened by tilting. A light waveguide is fed between the coupling parts of the sensor protection coupling, this waveguide being surrounded by a light waveguide protection element, the ends of which are fastened on the associated coupling parts of the sensor protection coupling.
A problem with this is, however, the lack of collision protection, or only minor collision protection, in the z direction, i.e. in the direction of the longitudinal axis of the probe element, so that damage can occur in the event of a sizeable perpendicular movement component. As mentioned, such solutions of the prior art may lead during the folding back to jamming processes of components, for example in the case of optical fibers, for which protective precautions must therefore be taken again. Furthermore, previous solutions do not allow effective damping of the separating or tilting processes.